A combination describes one way to select a subset of objects from a set of objects. For example, the number of ways to form a committee of 10 people from 100 people. The key difference between a permutation and a combination is that, in a permutation, once an object is used it can be used again. Permutations are relevant when sampling without replacement where order matters. Combinations are relevant when sampling without replacement where order does not matter. The number of combinations can be calculated using the [[Binomial Coefficient]].